The Center for Envi Presented in Partial Fulfillment of the Re Science in Enviro Addis Ababa

168 Pages·2017·2.66 MB·English

mposition, Structure, Diversity, Regeneration and Carbon
Stock in Weiramba Forest, Habru District, Northern Ethiopia: Implications
of Managing Forests for Biodiversity Conservation and Climate Change Mi-
Zelalem Teshager
A Thesis Submitted to
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Addis Ababa University
Addis Ababa, Ethiopia
SScchhooooll ooff GGrraadduuaattee SSttuuddiieess
March, 2017
Addis Ababa University
School of Graduate Studies
This is to certify that the thesis prepared by Zelalem Teshager, entitled: Woody Species Compo-
sition, Structure, Diversity, Regeneration and Carbon Stock in Weiramba Forest, Habru District,
Northern Ethiopia: Implications of Managing Forests for Biodiversity Conservation and Climate
Change Mitigation and submitted in partial fulfillment of the requirements for the Degree of
Master of Science in Environmental Science complies with the regulations of the University and
meets the accepted standards with respect to originality and quality.
Signed by examining committee:
Examiner ________________ signature ___________ Date____________
Examiner ________________ signature ___________ Date____________
Advisor _________________ signature ___________ Date____________
Advisor ________________ signature ___________ Date____________
___________________________________________________
Chair of Department or Graduate Program Coordinator
March, 2017
Addis Ababa, Ethiopia
Dedication
“This work is dedicated to my grandmother who let the ground for my current educational ca-
reers, but not alive today to see the finals and my Families, for their inspiration, love and support
throughout my life.”
ACKNOWLEDGMENT
First and for most I would like to thank God, Who makes everything possible. I am very grateful
to my advisors, Dr. Mekuria Argaw and Dr. Abeje Eshetie for their constructive criticisms,
comments, and unreserved efforts as needed in running this study. My thanks also go to Mr.
Dagne Yebeyen and Mr. Zewudu Yilma for providing me with all the information relevant to
this thesis.
I would like to express my gratitude to Central Ethiopia, Addis Ababa Environmental and Fore-
stry Research Center for the opportunity created and the research case team of Non-Timber For-
est Products in particular for facilitating my work and the funds provided.
I would also like to extend my deepest gratitude to Administrative staff member of Mersa Bu-
reau of Agriculture and Rural Development for providing secondary data.
I am grateful to all Researchers of Sirinka Agricultural Research Center especially, to Mr. Tigab
Redae, for their cooperation, unreserved support to have me access freely and in harmony with
the local farmers.
My deepest gratitude also goes to my friends who constantly supported and encouraged me with
several constructive ideas at different stages of this thesis work. Lastly, I would like to appreciate
my lovely families for their endless encouragement and support during the entire period.
Abstract
Woody Species Composition, Structure, Diversity, Regeneration and Carbon Stock in Wei-
ramba Forest, Habru District, Northern Ethiopia
Zelalem Teshager
Addis Ababa University, 2017
Climate change, caused by global warming, is the most pressing environmental problem of the
world today and it is a phenomenon partly resulting from abundance of carbon dioxide in the
atmosphere. The problem of increasing atmospheric carbon dioxide can be addressed in a num-
ber of ways. One of such actions is forestry development and forest management undertakings
that can contribute to mitigation.This study was conducted in Weiramba Forest, with the objec-
tives of estimating of the carbon stock and its variation along the environmental gradients, de-
termining the composition, structure, regeneration status and diversity of the vegetation found in
the area. A systematic sampling method was used to conduct the vegetation sampling. In order to
collect vegetation data a total of 40 quadrats, each with the size of 10 m x 20 m at an interval of
100 m, were laid along the established transects at 200 m apart. For the assessment of seedling
and sapling, two sub-quadrats each with the size of 2 m x 5 m were established at opposite sides
of the main quadrat. For litter and soil sample collection, five sub-quadrats each with the size of
1 m x 1 m were established at four corners and center of every quadrat. Plant Species Diversity
analysis was carried out by using Shannon Weiner index and Carbon stock was estimated by us-
ing allometric equations.The magnitude of the species diversity and carbon stock relationship
was analysed by using Pearson’s correlation. Results revealed that the total mean carbon stock
density of Weiramba Forest was 323.85 t/ha, of which 152.33 t/ha, 41.13 t/ha, 1.3 t/ha, 63.39
t/ha, 65.72 t/ha was contained in the above ground biomass, below ground biomass, litter bio-
mass, soil (0-20 cm depth) and (21-40 cm depth), respectively. Altitudinal gradient, slope and
aspect were the three environmental factors that affect the different carbon pools of the forest. A
total of 32 species representing 28 genera and 20 families were recorded in the forest. The
Shannon Weiner diversity index and evenness were resulted to be 2.30 and 0.66, respectively.
The plant species diversity and carbon stock relationship was small or weak positive. The popu-
lation structure revealed in diameter and height class frequency distribution was to be Bell-
shape with very high decrease towards the lower and higher diameter and height classes. The
total basal area of the forest was 32.10 m2/ha. The population structure of woody plants and the
regeneration status in the forest revealed that there is a need for conservation priority for spe-
cies with poor regeneration status. From the point of view of managing forests for climate
change mitigation and biodiversity conservation, the result suggested that the forest should be
conserved and protected in a sustainable way for further carbon sinks and biodiversity conserva-
tion.
Key words: Wiramba Forest, Environmental variables, Carbon stock, Diversity, Forest structure
TABLE OF CONTENTS
LIST OF FIGURES ................................................................................................................... v
LIST OF TABLES .................................................................................................................... vi
LIST OF APPENDICES ........................................................................................................ viii
LIST OF ACRONYMS / ABBREVIATIONS ......................................................................... ix
1. INTRODUCTION ................................................................................................................ 1
1.1 Background and Justification ........................................................................................... 1
1.2 Statement of the Problem and Significance of the Study ................................................. 4
1.3 Objectives of the Study .................................................................................................... 6
1.3.1 General Objective ...................................................................................................... 6
1.3.2 Specific Objectives .................................................................................................... 6
2. LITERATURE REVIEW ...................................................................................................... 7
2.1 Vegetation of Ethiopia ..................................................................................................... 7
2.1.1 Dry Evergreen Montane Forest of Ethiopia .............................................................. 8
2.2 Abundance, Frequency and important value index .......................................................... 9
2.3 Species diversity, species richness, evenness................................................................... 9
2.4 Regeneration and Recruitment Ecology of Forests ........................................................ 10
2.5 Greenhouse Gasses and Climate Change ....................................................................... 11
2.6 Impacts of Climate Change in Africa ............................................................................. 13
2.7 Impacts of Climate Change in Ethiopia ......................................................................... 14
2.8 Measurement Methods of Biomass and Carbon stock ................................................... 16
2.8.1 Aboveground Biomass and Carbon Measurement .................................................. 16
2.8.2 Below Ground Biomass and carbon Measurement ................................................. 17
2.8.3 Dead Litter biomass and carbon measurement ........................................................ 18
2.8.4 Dead wood carbon measurement ............................................................................. 19
i
2.8.5 Soil Organic Carbon Measurement ......................................................................... 19
2.9 Factors Influencing Carbon Stocks in Forest Ecosystems ............................................. 20
2.10 Global Carbon Cycle .................................................................................................... 21
2.11 Terrestrial Ecosystems carbon reservoir ...................................................................... 22
2.12 Kyoto Protocol ............................................................................................................. 24
2.13 Clean Development Mechanism (CDM)...................................................................... 25
2.14 Reducing Emissions from Deforestation and Forest Degradation ............................... 25
3. MATERIALS AND METHODS ......................................................................................... 27
3.1 Description of the Study Area ........................................................................................ 27
3.1.1 Geographical Location ............................................................................................ 27
3.1.2 Climate..................................................................................................................... 28
3.1.3 Vegetation ................................................................................................................ 28
3.1.4 Land Use Types ....................................................................................................... 28
3.1.5 Topography .............................................................................................................. 29
3.1.6 Soil ........................................................................................................................... 29
3.1.7 Economic Activity ................................................................................................... 29
3.2 Sampling and Data collection Methods ......................................................................... 30
3.2.1 Reconnaissance survey and study site selection ...................................................... 30
3.2.2 Study site boundaries Delineation ........................................................................... 30
3.2.3 Sample Size determination ...................................................................................... 30
3.2.4 Stratification of the Study Area ............................................................................... 31
3.2.5 Sampling design ...................................................................................................... 32
3.2.6 Data type .................................................................................................................. 33
3.2.7 Carbon Stock Measurement..................................................................................... 34
3.2.7.1 Tree Measurement ............................................................................................ 34
3.2.7.2 Litter Sampling ................................................................................................. 35
3.2.7.3 Soil Sampling .................................................................................................... 35
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3.3 Vegetation Data Analysis ............................................................................................... 36
3.3.1 Structural Analysis .................................................................................................. 36
3.3.2 Species Diversity Analysis ...................................................................................... 37
3.3.2.1 Evenness (Equitability) Analysis ...................................................................... 38
3.3.3 Regeneration status analysis of selected species ..................................................... 39
3.4 Carbon Stock Estimation in Different Carbon pools ..................................................... 40
3.4.1 Estimation of Carbon in the Aboveground Biomass ............................................... 40
3.4.2 Estimation of Carbon in the Belowground Biomass ............................................... 41
3.4.3 Estimation of Carbon in the Litter Biomass ............................................................ 42
3.4.4 Estimation of Carbon in Soil Organic Carbon (SOC) ............................................. 43
3.4.4.1 Soil Bulk Density Determination ...................................................................... 43
3.4.5 Estimation of Total Carbon Stock Density of the Area ........................................... 44
3.5 Statistical Analysis ......................................................................................................... 44
4. RESULTS AND DISCUSSION .......................................................................................... 46
4.1 Results ............................................................................................................................ 46
4.1.1 Woody Species Composition................................................................................... 46
4.1.2 Vegetation Structure ................................................................................................ 46
4.1.2.1 Density of Woody Species ................................................................................ 46
4.1.2.2 DBH and Height Distribution ........................................................................... 47
4.1.2.3 Frequency .......................................................................................................... 49
4.1.2.4 Basal Area (BA) ................................................................................................ 53
4.1.2.5 Importance Value Index (IVI) .......................................................................... 55
4.1.3 Species diversity, richness and equitability ............................................................. 57
4.1.4 Regeneration Status of Weiramba Forest ................................................................ 61
4.1.5 Biomass Stock in Above Ground and Below Ground ............................................. 63
4.1.6 Carbon Stock in the Different Carbon Pools ........................................................... 64
4.1.6.1 Carbon Stock in Above Ground Biomass (AGC) ............................................. 64
iii
4.1.6.2 Carbon Stock in Below Ground Biomass (BGC) ............................................. 68
4.1.6.3 Carbon Stock in Litter Biomass ........................................................................ 68
4.1.6.4 Soil Carbon Stock (SOC) .................................................................................. 69
4.1.7 Total Carbon Stock of Weiramba Forest ................................................................. 70
4.1.8 Comparison of Carbon Density in the Different Carbon Pools ............................... 73
4.1.9 Environmental factors versus Carbon Stock ........................................................... 73
4.1.9.1 Carbon Stocks of Different Pools along Altitudinal Variation ......................... 73
4.1.9.2 Carbon Stocks of Different Pools and Aspect .................................................. 75
4.1.9.3 Carbon Stocks of Different Pools and Slope .................................................... 76
4.1.10 Correlation between carbon stock and tree/shrub species diversity ...................... 78
4.2 Discussion ...................................................................................................................... 81
4.2.1 Woody Species Composition and Vegetation Structure.......................................... 81
4.2.1.1 Woody Species Composition ............................................................................ 81
4.2.1.2 Vegetation Structure ......................................................................................... 83
4.2.2 Carbon Stock in Different Carbon Pools ................................................................. 88
4.2.2.1 Biomass Potential of Weiramba Forest in different Carbon Pools ................... 88
4.2.2.2 Influence of Environmental Variables on Carbon Stock .................................. 92
4.2.3 Diversity versus Carbon stock ................................................................................. 96
5. CONCLUSION AND RECOMMENDATIONS ................................................................ 97
5.1 Conclusion ...................................................................................................................... 97
5.2 Recommendations .......................................................................................................... 99
REFERENCES ...................................................................................................................... 101
APPENDICES ....................................................................................................................... 123
iv
LIST OF FIGURES
Figure 1: The greenhouse effect. Source:www.epa.gov/climatechange/science:index.html .. 13
Figure 2: Graphical representation of the different forest carbon pools. ................................. 20
Figure 3: Illustration of A sub-cycle within the global carbon cycle. ..................................... 24
Figure 4: Map of the study area ............................................................................................... 27
Figure 5: Design of main and sub-quadrats for sampling of carbon pools .............................. 33
Figure 6: Design of sub quadrats for Litter Sampling ............................................................. 35
Figure 7: DBH class distribution of all trees recorded in the study area ................................. 48
Figure 8: Height class distribution of all trees recorded in the study area ............................... 49
Figure 9: Sapling and Seedling numbers of each species ........................................................ 61
Figure 10: Density percentage of seedlings, saplings and mature of tree species in the study
area ........................................................................................................................................... 62
Figure 11: AGB and BGB versus Quadrats ............................................................................. 63
Figure 12: AGC and AG CO versus Quadrats ....................................................................... 64
2
Figure 13: BGC and BG CO versus quadrats ......................................................................... 68
2
Figure 14: LC and L CO versus Quadrats .............................................................................. 69
2
Figure 15: SOC and S (CO ) versus quadrats in depth 0-20 cm .............................................. 70
2
Figure 16: SOC and S (CO ) versus Quadrats in depth 21-40 cm ........................................... 70
2
Figure 17: Total Carbon per Quadrat ....................................................................................... 71
Figure 18: Correlation of tree/shrub species diversity and carbon stock. ................................ 80
v